1. Field of the Invention
The present invention relates generally to user interfaces for information collection devices and, more particularly, to a data collection device configured to collect, store and display information in relation to the time at which the information is collected.
2. Background
A user interface is something which bridges the gap between a human user who seeks to control a device and the hardware and/or software which actually controls the device. The familiar keypad of a touch tone telephone and the alphanumeric keyboard associated with a personal computer are such user interfaces. In addition to hardware components, graphical user interfaces have become an increasingly common feature of personal computers. Such interfaces are provided either as built-in portions of the computer operating system, as in the case of the Macintosh computer available from Apple Computer Inc. of Cupertino, Calif., or as add-on software products that can be purchased separately.
Regardless of whether the user interface is a hardware device or a software program (or, as is increasingly the case, a combination of both), the purpose of the user interface is, as indicated, to bridge the gap between the human operator and the device being utilized. For example, graphical user interfaces used with personal computers often have the ability to initiate execution of other, so-called, "applications programs". Examples of application programs might be spreadsheets, word processing programs, database programs, etc. The process of initiating execution of an application program is typically handled through the use of small graphical symbols known as "icons". The graphical user interface displays the icons on the computer screen, one icon for each application program that can be run. The human user initiates execution of an application program by selecting the corresponding icon, most often using a pointing device such as a mouse.
A conventional graphical user interface such as described above significantly reduces the amount of information that a user must recall in order to effectively use the computer. For example, instead of remembering the name of an application program, and the location of the program on a particular disk, the user need only remember that a particular icon is associated with the application program.
Like their graphical counterparts, hardware user interfaces also allow for ease of operation. For example, the familiar mouse associated with a personal computer allows a user to position the cursor and select from among the various icons displayed on a screen. By using the mouse the user is able to avoid having to perform a number of complex keystrokes.
An example of a user interface of potentially immense utility is in conjunction with a data collection device used by a field worker while collecting information in remote location. For example, surveying property to record information on features such as boundaries and artifacts located on the property could be facilitated with a convenient user interface. Collecting information while out on a data collection project by using any means other than electronic collection devices requires extensive note taking in journals or maps that makes it cumbersome to perform the collection and recording task.
It is often useful to be able to record data and notes on electronic devices such as portable computers, notebooks, or simple electronic recording devices to simplify the effort a field worker must perform to record data. The data collected can then be stored for later retrieval by a parent system that can be used to disseminate and interpret the data into useful information for decision making. In many of these applications, a time based record of the data collected would be quite useful for tracking factors such as productivity of the data collecting technicians, the qualities related to changing data over time as well as other factors. Data collecting devices that incorporate measuring instruments such as land surveying devices known as Total Stations, Laser range-finders, direction finding beacons, compasses, tape measures and other such devices would be greatly improved if they had the capability of noting the time when the date it was collected.
A surveying device that collects data pertaining to artifacts located on real property such as trees and buildings as well as to boundaries, both natural and artificially defined would be greatly improved by a device that was able to collect, display and record data with reference to the time at which the data was collected. If available in real time the information could then be used by the operator in the field to track the data collection to ensure an organized and complete survey. The information could also be used by the operator as well as management overseeing the operator to modify the operator's operation for higher efficiency by reducing the time required to collect data as well as organizing and keeping track of data collected. Furthermore, the information would be a useful archival record of a property's physical history. The introduction of advanced geographic location systems such as a global positioning system could add another dimension to the survey operator's capability.
The global positioning system (GPS) is a multiple satellite based radio positioning system in which each GPS satellite transmits data that allows a user to precisely measure the distance from selected ones of the GPS satellites to his or her receiver antenna and, thereafter, to compute position, velocity, and time parameters to a high degree of accuracy using known triangulation techniques. The signals provided by the GPS satellites can be received both globally and continuously.
In general, each GPS satellite transmits signals on two frequencies known as L1 and L2. The signals are transmitted using spread spectrum techniques that employ two types of spreading functions. Course acquisition (C/A) and precise (P) pseudorandom noise (PRN) codes are transmitted on frequency L1 and the P code only is transmitted on frequency L2. The C/A code is available to any user, military or civilian, however, the P code is available only to authorized military and civilian users. Both the P and C/A codes contain data that enable a receiver to determine the range between a selected satellite and the user. Superimposed on both the P and the C/A codes is the navigation message. The navigation message contains GPS system time; a hand over word used in connection with transitioning from C/A code to P code tracking; ephemeris data for the particular satellite being tracked; and almanac data for all the satellites in the GPS constellation.
GPS finds use in a wide variety of applications, including space, air, sea and land vehicle navigation, precise positioning, time transfer, attitude reference, surveying, etc. Within these various disciplines, a number of prior GPS receivers are known. These include sequential tracking receivers, continuous reception receivers, multiplexing receivers, all-in-view receivers, time transfer receivers, and surveying receivers.
GPS receivers typically comprise a number of subsystems. These include an antenna assembly, an RF assembly, and a GPS processor assembly. The antenna assembly receives the L-band GPS signal and amplifies it prior to insertion into the RF assembly. The RF assembly mixes the L-band GPS signal down to a convenient intermediate frequency (IF). Then, using various known techniques, the PRN code modulating the L-band signal is tracked through code correlation to measure the time of transmissions of the signals from the satellite. The Doppler shift of the received L-band signal is also measured through a carrier tracking loop. The code correlation and carrier tracking functions can be performed using either analog or digital processing means.
The control of the code and carrier tracking loops is provided by the GPS processor assembly. By differencing this measurement with the time of reception, as determined by the receiver's clock, the pseudo range between the receiver and the satellite being tracked may be determined. This pseudo range includes both the range to the satellite and the offset of the receiver's clock from the GPS master time reference. The pseudo range measurements and navigation data from four satellites are usually sufficient to compute a three-dimensional position and velocity fix, to calibrate the receiver's clock offset, and to provide an indication of GPS time.
In some known receivers, the receiver processor controller functions are performed using a computer separate from that on which the navigation functions are performed. In other known receivers, both types of functions are performed by a single processor. Regardless of the system used, the receiver processor controller functions typically include monitoring channel status and control, signal acquisition and reacquisition, code and carrier tracking loops, computing pseudo range and delta range measurements, determining data hedge timing, acquisition and storage of almanac and ephemeris data broadcast by the satellites, processor control and timing, address and command decoding, timed interrupt generation, interrupt acknowledgment control, and GPS timing.
Known GPS receivers also perform navigation processing functions including satellite orbit calculations and satellite selection, atmosphere delay correction calculations, navigation solution computation, clock bias and rate estimates, computation of output information, and preprocessing and coordinate conversion of aiding information.
The GPS standard positioning service provides a navigation accuracy of 100 meters. A number of applications of GPS (including surveying) require higher levels of accuracy. Accuracy can be improved using a technique known as differential GPS. This technique involves operating a GPS receiver and a known location. The receiver is used to compute satellite pseudo range correction data using prior knowledge of the correct satellite pseudo ranges, which are then broadcast to users in the same geographic area. The pseudo range corrections are incorporated into the navigation solution of another GPS receiver (a remote receiver) to correct the observed satellite pseudo range measurements, thereby improving the accuracy of the position determination of the remote. Correlation of the errors experienced at the reference station and at the remote is dependent upon the distance between them, however they are normally highly correlated for a user within 350 kilometers of the reference station.
As indicated above, GPS receivers have been used to aid in the surveying process. In the past, a surveyor could take a GPS receiver into the field, position the receiver's antenna at a desired location, switch on the receiver to gather position data for the given location, and ultimately arrive at a location fix for the position of the GPS receiver's antenna. Very often, such surveying techniques are carried out in conjunction with city planning operations, such as the monitoring of the condition of city assets, often referred to in the trade as artifacts, for example, utility poles, manhole covers, etc. Thus, a surveyor could position his GPS receiver antenna over a manhole cover and determine a location fix for the manhole cover and other information of interest. At the same time, the surveyor could record in a field notebook the condition of the manhole cover. Collecting data pertaining to the artifacts is referred to in the profession as "capturing" the artifacts. Later, in an office setting, the position information could be correlated with the condition information for the manhole cover and similar results for other city artifacts could be combined together to produce an overall report for the city engineers or other interested persons regarding the location and condition of the manhole covers.
The above process is not only time consuming, but there exists the danger that the surveyor's notebook will be lost or the data will not be accurately transferred from the notebook to the report. For example, location data associated with one artifact may be improperly associated with attribute information for a different artifact. Accordingly, a need exists for a single surveying apparatus which can compile and associate position information for an artifact of interest together with other attribute information in the field environment. A user interface would also be useful in helping the surveyor in the field to organize the survey logistics as well as the data collected.
For the surveying process discussed above, it would be useful to the user as well as managing personnel to record in a time based record the events of a particular survey using a helpful user interface that can streamline the process of collecting data for a series of artifacts. It would be useful to have a record of not only what was surveyed, but also the time that was spent on each artifact recorded in the field. During the data collection activities, the surveyor in the field could know whether enough time has passed to achieve the proper accuracy of position for a given artifact. Furthermore, particular surveys could be investigated regarding whether enough time was spent at a particular artifact in order to achieve the proper accuracy of position, whether too much time was wasted in gathering useless information, or whether a particular surveyor in the field is properly performing his duties. It would also be useful to give the surveyor in the field a real time map to refer to in order help keep track of the survey project as a whole. In combination with the time based record, the field worker could even backtrack and take new measurements of artifacts that were inaccurately gathered at an earlier point in time. The time based information could also serve as a useful archival record of changing conditions in a surveyed field over time. As will be seen in the specification below, the present invention addresses these needs in a novel and elegant manner.